Abstract This proposal focuses on the decapping and deadenylation of mRNA. Decapping is the removal of the 5' cap structure is an important step in the regulation of mRNA. The turnover of mRNA is intimately connected to the process of protein synthesis. Importantly, work from this grant has documented that factors involved in destroying mRNAs are themselves regulators of ribosome function. Specifically, a key component of the decapping complex called DHH1 slows ribosome translocation and this event serves to stimulate removal of the 5' cap and degradation of the transcript body. The first Aim of this grant is designed to understand how DHH1 alters ribosome function. This proposal also focuses on deadenylation of mRNA. Deadenylation is the removal of the 3' poly(A) tail on an mRNA and required before mRNA decapping can occur. Aim 2 of this grant focuses on understanding how deadenylation and decapping are coupled. Deadenylation is also thought to be the rate-limiting step in mRNA turnover. Importantly, deadenylation rates are variable between mRNA species but how these heterogeneity is achieved is unclear. Aim 3 of this proposal is to determine how differential deadenylation rates occur. Together, these Aims highlight the importance of the decapping and deadenylase enzymes in controlling a diversity of gene expression events.